One major objective is the use of monoclonal antibodies to assess the structural relationship between histocompatibility and tumor associated antigens on murine tumor cells and to examine possible H-2 viral interactions. Efforts will also be made to further chracterize the immunological and molecular profiles of H-2 and Ia antigens with cross reactive anti-HLA antibodies. The other major objective of our studies is to continue our ongoing efforts to delineate the cellular and molecular heterogeneity of H-2 and Ia antigen on murine cells with monoclonal antibodies.